The antibiotic of the subject application is produced by the controlled fermentation of the microorganism Streptomyces ficellus Dietz, sp. n., NRRL 8067. Previously, as disclosed in application Ser. No. 542,226, filed on Jan. 20, 1975, the subject fermentation was found to produce the new antibiotic U-47,929. Subsequently, the same fermentation was found to produce the new antibiotic U-48,266, and this is disclosed in application Ser. No. 556,573, filed on Mar. 10, 1975. The antibiotic produced by the process of the subject invention, U-51,640, has been found to be identical to nojirimycin (J. Antibiotics 20:66 -71, 1967) the structure of which is presented by l ##STR1##